--- a/src/event/ngx_event_timer.c
+++ b/src/event/ngx_event_timer.c
@@ -10,13 +10,8 @@
 #include <ngx_event.h>
 
 
-#if (NGX_THREADS)
-ngx_mutex_t  *ngx_event_timer_mutex;
-#endif
-
-
-ngx_thread_volatile ngx_rbtree_t  ngx_event_timer_rbtree;
-static ngx_rbtree_node_t          ngx_event_timer_sentinel;
+ngx_rbtree_t              ngx_event_timer_rbtree;
+static ngx_rbtree_node_t  ngx_event_timer_sentinel;
 
 /*
  * the event timer rbtree may contain the duplicate keys, however,
@@ -30,20 +25,6 @@ ngx_event_timer_init(ngx_log_t *log)
     ngx_rbtree_init(&ngx_event_timer_rbtree, &ngx_event_timer_sentinel,
                     ngx_rbtree_insert_timer_value);
 
-#if (NGX_THREADS)
-
-    if (ngx_event_timer_mutex) {
-        ngx_event_timer_mutex->log = log;
-        return NGX_OK;
-    }
-
-    ngx_event_timer_mutex = ngx_mutex_init(log, 0);
-    if (ngx_event_timer_mutex == NULL) {
-        return NGX_ERROR;
-    }
-
-#endif
-
     return NGX_OK;
 }
 
@@ -58,15 +39,11 @@ ngx_event_find_timer(void)
         return NGX_TIMER_INFINITE;
     }
 
-    ngx_mutex_lock(ngx_event_timer_mutex);
-
     root = ngx_event_timer_rbtree.root;
     sentinel = ngx_event_timer_rbtree.sentinel;
 
     node = ngx_rbtree_min(root, sentinel);
 
-    ngx_mutex_unlock(ngx_event_timer_mutex);
-
     timer = (ngx_msec_int_t) (node->key - ngx_current_msec);
 
     return (ngx_msec_t) (timer > 0 ? timer : 0);
@@ -82,9 +59,6 @@ ngx_event_expire_timers(void)
     sentinel = ngx_event_timer_rbtree.sentinel;
 
     for ( ;; ) {
-
-        ngx_mutex_lock(ngx_event_timer_mutex);
-
         root = ngx_event_timer_rbtree.root;
 
         if (root == sentinel) {
@@ -104,8 +78,6 @@ ngx_event_expire_timers(void)
 
             ngx_rbtree_delete(&ngx_event_timer_rbtree, &ev->timer);
 
-            ngx_mutex_unlock(ngx_event_timer_mutex);
-
 #if (NGX_DEBUG)
             ev->timer.left = NULL;
             ev->timer.right = NULL;
@@ -123,6 +95,4 @@ ngx_event_expire_timers(void)
 
         break;
     }
-
-    ngx_mutex_unlock(ngx_event_timer_mutex);
 }